Model confirmation of the MS-Related Symptom Checklist.

Data from a 26-item self-administered MS-Related Symptom Checklist (MS-RS), designed for persons diagnosed with multiple sclerosis (MS), were factored for the purpose of (a) providing further validity for the MS-RS Checklist, (b) determining structural relationships between and within MS symptom clusters, and (c) determining conceptual similarities between symptoms contained within the MS-RS model and those associated with eight neurological functional systems. Data analyses were based on 491 MS subjects. Principal component analysis and Varimax-rotated factor analysis were used to achieve scale parsimony. The resultant 22-item scale consisting of five factors was subjected to confirmatory factor analysis to determine relationships among factors, observed variables, and residual variance within the factor model. Modification of the initial factor model resulted in the inclusion of one additional relationship between an observed variable and a second factor and six paired relations among the residual variances. The modified factor model had a satisfactory GFI of .910. Signs and symptoms contained within the five-factor solution compared favorably with signs and symptoms assigned to the neurological functional systems which are used clinically in classifying MS disease impairment.